Adding rivets to an object for 3D printing
You could model this, if you're starting with  a topology something like the  one illustrated here:

With Pivot set to 'Individual Origins'


CtrlR add three edge-loops
AltP poke the two middle face-rings
Select a couple of consecutive rivet-vertices (not necessarily just one apart)  on the central loop - use CtrlShiftNumpad+ to select the rest, and then CtrlShiftB bevel those vertices, in 'Offset' mode
Space .. look up the 'Circle' operator, and use it on your newly created faces. (They should still be selected)
perform whichever series of insets, extrudes, and scales create the kind of rivets you want.




I don't know whether you're sub-d modelling, but this is the result after putting on a level of subdivision.



You could use the Loop Tools add-on > 'Space' option at the vertex stage, in various ways, if you want to improve the distribution of rivets. 

Although the result is not all quads (before subdivision), it's in the flat, for printing, and is not expected to deform, so that's probably OK?